Earlier today, Mailbox received another update. To be sure, the new update is but a minor one. But it does deliver some bug fixes for the "account reset issue" that has been plaguing many users of the popular email app.
According to the Mailbox team, the issue has been affecting a significant number of users of the app's recently released versions for iOS 7: versions 1.6 and 1.6.1.
Basically, the issue causes Gmail accounts on Mailbox to be logged out of their own accord. Subsequently, it causes affected users to get frustrated, especially in cases where their accounts are repeatedly logged out.
As it turns out, the pesky bug appears to be rooted in the new Background App Refresh feature in iOS 7, which is supported in versions 1.6 and 1.6.1 of Mailbox. The Mailbox team notes in a new blog post:

Much of our team has spent the last five days in crisis mode trying to diagnose the bug, and we currently believe the root cause lies somewhere in our interaction with Apple’s new Background Refresh feature. We’ve submitted a ticket to Apple and are currently discussing the problem with their support team. We’re also having discussions with a couple other prominent apps that are seeing similar issues.

One of these apps, notes The Verge, is the popular photo messaging app Snapchat.
As for Mailbox, it has just been updated to version 1.6.2. This new version "disables background refresh to temporarily bypass the problem," according to the Mailbox team, which promises to "keep working with Apple and the developer community for a more long-term fix."
If you're among those who have been affected by the aforementioned account reset issue, you're advised to update to the latest version of Mailbox, which is available now in the App Store for free.